1. Field
Embodiments relate to semiconductor devices and methods of fabricating the same.
2. Description of the Related Art
Semiconductor memory devices used to store data may be classified into volatile memory devices and nonvolatile memory devices. The volatile memory devices lose the stored data when power is interrupted. However, the nonvolatile memory devices are capable of retaining the stored data even when power is interrupted.
In general, the nonvolatile memory devices are capable of electrically erasing and programming data and capable of storing the data even when power is interrupted. In recent years, accordingly, the nonvolatile memory devices have increasingly been used in various fields.
These nonvolatile memory devices are configured with various types of memory cell transistors. The nonvolatile memory devices are categorized into NAND-type nonvolatile memory devices and NOR-type nonvolatile memory devices according to a cell array structure. The NAND-type nonvolatile memory devices and the NOR-type nonvolatile memory devices have an advantage and a disadvantage in terms of high integration and high-speed performance, respectively.
In particular, the NAND-type nonvolatile memory devices may be advantageous in high integration due to a cell string in which a plurality of memory cell transistors are connected to each other in series. Moreover, information update speed of the NAND-type nonvolatile memory devices is considerably faster than that of the NOR-type nonvolatile memory devices, since the NAND-type nonvolatile memory devices may simultaneously change all information stored in the plurality of memory cell transistors. Due to the high integration and the fast information update speed, the NAND-type nonvolatile memory devices are mainly used in portable devices using a mass storage device, e.g., a digital camera or an MP3 player.